import InlineWorker from "inline-worker"

export class Recorder {
    config = {
        bufferLen: 4096,
        numChannels: 2,
        mimeType: "audio/wav"
    }

    recording = false

    callbacks = {
        getBuffer: [],
        exportWAV: []
    }

    constructor(source, cfg) {
        Object.assign(this.config, cfg)
        this.context = source.context
        this.node = (
            this.context.createScriptProcessor ||
            this.context.createJavaScriptNode
        ).call(
            this.context,
            this.config.bufferLen,
            this.config.numChannels,
            this.config.numChannels
        )

        this.node.onaudioprocess = e => {
            if (!this.recording) return

            var buffer = []
            for (
                var channel = 0;
                channel < this.config.numChannels;
                channel++
            ) {
                buffer.push(e.inputBuffer.getChannelData(channel))
            }
            this.worker.postMessage({
                command: "record",
                buffer: buffer
            })
        }

        source.connect(this.node)
        this.node.connect(this.context.destination) //this should not be necessary

        let self = {}
        this.worker = new InlineWorker(function() {
            let recLength = 0,
                recBuffers = [],
                sampleRate,
                numChannels

            this.onmessage = function(e) {
                switch (e.data.command) {
                    case "init":
                        init(e.data.config)
                        break
                    case "record":
                        record(e.data.buffer)
                        break
                    case "exportWAV":
                        exportWAV(e.data.type)
                        break
                    case "getBuffer":
                        getBuffer()
                        break
                    case "clear":
                        clear()
                        break
                }
            }

            function init(config) {
                sampleRate = config.sampleRate
                numChannels = config.numChannels
                initBuffers()
            }

            function record(inputBuffer) {
                for (var channel = 0; channel < numChannels; channel++) {
                    recBuffers[channel].push(inputBuffer[channel])
                }
                recLength += inputBuffer[0].length
            }

            function extractSingleChannel(input) {
                var sampleStep = 3
                //如果此处不按比例缩短，实际输出的文件会包含sampleStep倍长度的空录音
                var length = Math.ceil(input.length / sampleStep)
                var result = new Float32Array(length)
                var index = 0,
                    inputIndex = 0
                while (index < length) {
                    //此处是处理关键，算法就是输入的数据点每隔sampleStep距离取一个点放入result
                    result[index++] = input[inputIndex]
                    inputIndex += sampleStep
                }
                return result
            }

            function exportWAV(type) {
                let buffers = []
                for (let channel = 0; channel < numChannels; channel++) {
                    buffers.push(mergeBuffers(recBuffers[channel], recLength))
                }
                let interleaved
                if (numChannels === 2) {
                    interleaved = interleave(buffers[0], buffers[1])
                } else {
                    interleaved = extractSingleChannel(buffers[0])
                }
                let dataview = encodeWAV(interleaved)
                let audioBlob = new Blob([dataview], { type: type })

                this.postMessage({ command: "exportWAV", data: audioBlob })
            }

            function getBuffer() {
                let buffers = []
                for (let channel = 0; channel < numChannels; channel++) {
                    buffers.push(mergeBuffers(recBuffers[channel], recLength))
                }
                this.postMessage({ command: "getBuffer", data: buffers })
            }

            function clear() {
                recLength = 0
                recBuffers = []
                initBuffers()
            }

            function initBuffers() {
                for (let channel = 0; channel < numChannels; channel++) {
                    recBuffers[channel] = []
                }
            }

            function mergeBuffers(recBuffers, recLength) {
                let result = new Float32Array(recLength)
                let offset = 0
                for (let i = 0; i < recBuffers.length; i++) {
                    result.set(recBuffers[i], offset)
                    offset += recBuffers[i].length
                }
                return result
            }

            function interleave(inputL, inputR) {
                let length = inputL.length + inputR.length
                let result = new Float32Array(length)

                let index = 0,
                    inputIndex = 0

                while (index < length) {
                    result[index++] = inputL[inputIndex]
                    result[index++] = inputR[inputIndex]
                    inputIndex++
                }
                return result
            }

            function floatTo16BitPCM(output, offset, input) {
                for (let i = 0; i < input.length; i++, offset += 2) {
                    let s = Math.max(-1, Math.min(1, input[i]))
                    output.setInt16(
                        offset,
                        s < 0 ? s * 0x8000 : s * 0x7fff,
                        true
                    )
                }
            }

            function writeString(view, offset, string) {
                for (let i = 0; i < string.length; i++) {
                    view.setUint8(offset + i, string.charCodeAt(i))
                }
            }

            function encodeWAV(samples) {
                let buffer = new ArrayBuffer(44 + samples.length * 2)
                let view = new DataView(buffer)

                /* RIFF identifier */
                writeString(view, 0, "RIFF")
                /* RIFF chunk length */
                view.setUint32(4, 36 + samples.length * 2, true)
                /* RIFF type */
                writeString(view, 8, "WAVE")
                /* format chunk identifier */
                writeString(view, 12, "fmt ")
                /* format chunk length */
                view.setUint32(16, 16, true)
                /* sample format (raw) */
                view.setUint16(20, 1, true)
                /* channel count */
                view.setUint16(22, numChannels, true)
                /* sample rate */
                view.setUint32(24, sampleRate, true)
                /* byte rate (sample rate * block align) */
                view.setUint32(28, sampleRate * 4, true)
                /* block align (channel count * bytes per sample) */
                view.setUint16(32, numChannels * 2, true)
                /* bits per sample */
                view.setUint16(34, 16, true)
                /* data chunk identifier */
                writeString(view, 36, "data")
                /* data chunk length */
                view.setUint32(40, samples.length * 2, true)

                floatTo16BitPCM(view, 44, samples)

                return view
            }
        }, self)

        this.worker.postMessage({
            command: "init",
            config: {
                sampleRate: this.context.sampleRate,
                numChannels: this.config.numChannels
            }
        })

        this.worker.onmessage = e => {
            let cb = this.callbacks[e.data.command].pop()
            if (typeof cb == "function") {
                cb(e.data.data)
            }
        }
    }

    record() {
        this.recording = true
    }

    stop() {
        this.recording = false
    }

    clear() {
        this.worker.postMessage({ command: "clear" })
    }

    getBuffer(cb) {
        cb = cb || this.config.callback
        if (!cb) throw new Error("Callback not set")

        this.callbacks.getBuffer.push(cb)

        this.worker.postMessage({ command: "getBuffer" })
    }

    exportWAV(cb, mimeType) {
        mimeType = mimeType || this.config.mimeType
        cb = cb || this.config.callback
        if (!cb) throw new Error("Callback not set")

        this.callbacks.exportWAV.push(cb)

        this.worker.postMessage({
            command: "exportWAV",
            type: mimeType
        })
    }

    static forceDownload(blob, filename) {
        let url = (window.URL || window.webkitURL).createObjectURL(blob)
        let link = window.document.createElement("a")
        link.href = url
        link.download = filename || "output.wav"
        let click = document.createEvent("Event")
        click.initEvent("click", true, true)
        link.dispatchEvent(click)
    }
}

export default Recorder
